"هَل أَنْتِ مُهَنْدِسة أُرْدُنِيّة يا أَرْوى؟"
Translation:Are you a Jordanian engineer, Arwa?
"An engineer" is in the indefinite format, due to the word 'an'. Duo hasn't explained yet prior to this lesson, but the "tun" sound after the noun and its adjective indicate an indefinite format. This grammatical usage is called Tanwin and it has three sounds: "un", "an" and "in". Each sound indicates whether the word is in the nominative, accusative or genitive case. "Un" represents the nominative case.
It may seem like a very simple question, but it requires a very complicated answer that delves deep into the dark hole of Arabic grammar and the art of reading Arabic. A short answer is to read up on it later, but for now to know that you do NOT pronounce these when speaking with someone. These are only pronounced while reading texts.